1. Field of the Invention
The present invention relates to a recording medium take-up mechanism and a printer.
2. Description of the Related Art
A printer having a rotatable take-up shaft has conventionally been known, which winds a recording medium, such as paper, onto the take-up shaft after printing. JP 2009-143147 A and WO/2010/087012 describe such a printer.
In JP 2009-143147 A and WO/2010/087012, the printer has a take-up shaft disposed below a platen, a cylindrical tension bar disposed frontward relative to the platen and the take-up shaft, and a pivotable support arm for supporting the tension bar. The tension bar imparts tension to the recording medium by pressing the back surface of the recording medium having been printed. The recording medium moves from the platen onto the tension bar, and thereafter it is wound around the take-up shaft. The support arm is pivotable about a support shaft that supports the support arm. As the support arm pivots about the support shaft, the tension bar swings about the support shaft. When the position of the tension bar is invariable, the tension imparted to the recording medium is constant. In the above-described printer, the rotation of the take-up shaft is controlled so that the position of the tension bar falls within a predetermined position range. This suppresses variations in the tension of the recording medium.
When the tension bar moves, the tension of the recording medium changes temporarily. In the conventional printers, the change in the tension of the recording medium is likely to be different from a portion of the recording medium to another. As a consequence, there has been a problem that the recording medium tends to be twisted easily when it is wound. When the recording medium is twisted, the problem arises that the recording medium cannot be wound around the take-up shaft in a desirable manner. Moreover, when the recording medium is twisted during winding, printing may not be carried out desirably because the recording medium is twisted on the platen.